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22 October 2013:Twenty-two thousand trips around the planet

Four years after its launch, Swisscube, the small satellite developed by EPFL’s Space Center, is still in operation. Some of the technological choices made and considered audacious at the time have yielded valuable lessons for building future spacecraft.

The mission was supposed to last three months to one year, but now, four years later, Swisscube is still orbiting the Earth. This small Cubesat-type satellite, measuring just 10cm by 10cm and entirely designed in Switzerland, was launched on September 23, 2009. After more than 22,000 trips around the planet, all its functions are still operational. Only one of its six solar sensors has been irreversibly damaged.

The satellite’s mission was to photograph “air glow,” a photoluminescence phenomenon that occurs in the upper atmosphere and is caused by the interaction between solar radiation and oxygen molecules. In four years, some 250 images were produced. Even though these data are not precise enough to be studied scientifically, the Swiss space community still considers Swisscube a success.

“Its goal was above all educational,” says Muriel Richard, an engineer at the Swiss Space Center and Swisscube project manager. “It allowed nearly 200 students from EPFL and the Universities of Applied Science to learn about space technology. And today, it’s still valuable for current students as an extraordinary experimentation platform, with which we can, for example, check movements and altitude or test ground-based algorithms.”

Put to the test
The fact that it’s lasted this long proves that the satellite is robust. It confirms the wisdom of certain technological choices that were made; at the time they seemed audacious, but now, in hindsight, they have proven innovative and full of lessons that can be drawn upon for the construction of future spacecraft. For example, it was decided that instead of components that were certified space-quality, standard electronic components would be used; they were thus much less expensive, such as mobile phone batteries bundled into a thermally controlled, waterproof housing. An innovative system of copper mountings was developed that both secured the solar cells to the external walls, ensuring stowage during the violent shakings of launch.

“The first week is decisive,” explains Richard. “If the satellite gets through it without a hitch, it’s because it was truly well built, and there’s a high likelihood that it will operate for years to come.” Once the satellite reaches space, the electronics on board are seriously put to the test. To start with, vibrations experienced during the launch will reveal even the slightest error in soldering. The materials also undergo temperature variations that can range from -50 to 70 degrees Celsius. Solar radiation and the flow of solar particles can also easily damage systems that are insufficiently protected. And then there’s always the chance of collision with the ever-increasing amount of space debris orbiting the Earth.

Set your calendar for 2018
In fact, Swisscube has narrowly avoided impact several times. As soon as it was launched, it was quickly caught up in the train of debris created by the February 2009 collision between the commercial satellite Iridium-33 the Russian satellite Cosmos-2251. More recently, on September 11, 2013, US Air Force alerted the Swiss Space Center that its Cubesat passed less than 75 meters away from one of the 15,000 pieces of space debris more than 10cm in diameter that have been identified and are monitored from the ground by the U.S.. But it appears that Swisscube’s time has not yet come. Barring an unforeseen event, Swisscube’s demise has been programmed for 2018. It will be the first object captured and destroyed by CleanSpace One, the space debris clean-up satellite currently under development at the Space Center.

15 February 2012:

Today during a press conference, the Swiss Space Center announced the birth of a new NanoSat project called CleanSpace One.

The objectives of the CleanSpace One project are to:

- Increase awareness, responsibility in regard to orbital debris and educate young people

- Demonstrate technologies related to Orbital Debris Removal

- De-orbit a known and politically acceptable debris.

A good a probable target for debris removal will be SwissCube.
For more info, check the web site space.epfl.ch.

2 December 2011:

During its annual meeting, the Space Center EPFL, to be renamed soon Swiss Space Center,
announced the closing of the Swisscube project.
A review of the fruitful year 2011 was presented and can be found here.
This closing will allow the Space Center to focus its efforts on a new mission.
The operations have been successfully transferred to interested Radio-Amateurs, in particular HB9MFL.
They have been trained and are now able to command the satellite autonomously.
Any other radio-amateur interested, please contact us.

23 September 2011:

Today we celebrate the two years of SwissCube in orbit! As all the data that we receive show no indication of weakness on board the spacecraft, there is no reason it should not continue.
Many thanks to all those who helped us achieved this milestone!

The chocolate model shown on the photo has been made for a SwissCube designer's celebration. The other model on his side is a regular one.

24 Mars 2011:

SwissCube downloads images and satisfies its scientific objective. Check this out :

SwissCube is now in space for more than 300 days! The power and beacon systems are still doing very well. We decode the beacon on a daily basis. The data confirm that we have enough energy onboard to keep communicating with the satellite multiple times every day. We also collect the housekeeping from the COM board during almost every passes we operate.

The semester project of Federico showed some weaknesses in the decoding of the uplink onboard the satellite. It also helped us to understand how to improve our method for commanding the satellite. Based on these results, we discovered that the high data rate communication link works better than we thought.

Now, we are investigating another lead to explain the decrease of the number of packets received. We think that the internal bus or the controllers of this bus do not work properly. In order to understand this degradation, we are collecting experiences from other teams with the I2C bus. Until now, we do not have a simple explanation that we can prove.

On the ground segment side, we finally fixed the motors of our antenna a few days ago. We are back to a completely operational state at EPFL. Two weeks ago, we visited the team from Fribourg and their facilities. We thank them again for welcoming us and for their support in the operations, especially when we were unable to command from EPFL.

Also, we are expanding our operation capabilities. The ground station of our partner in the Netherlands, EATOPS, is on a good way. We are looking forward to see it in action. We are trying a beta version of the GENSO network too (www.genso.org). It seems very promising but there are not enough active ground stations at this moment to operate the satellite on a regular basis. We hope this network will grow soon. We have performed some tests with the HERMES antenna of the Ecuadorian civilian space agency. We already listened to SwissCube from this antenna during the close approach in January. We also plan to command the satellite through this antenna in Ecuador.

Last week, we did statistics with the data received from the radio amateurs. Here are some interesting numbers. Since the launch, the radio amateurs community has forwarded 13319 beacon messages and 6994 frames. Special thanks to HB9MFL, DK3WN and F6BYJ. The beacon messages quoted here are only messages saved in our database. Many more have been decoded through the Web site. We always appreciate these messages because they help us to decide whether we command during pass or not based on the health of the satellite.

In the upcoming months, we will continue to investigate the internal bus issue. We also would like to start the payload and downlink the archive from the EPS. Then, we will integrate the new operation capabilities to our main network.

After 222 days of life in space, SwissCube is still working quite well. We have started to see some degradation in the high data rate communication link, but other critical functions such as beacon and power management are doing excellent. You will find some of the data showing the health of the satellite in the attached file. Federico, a student from EPFL, is trying to understand and characterize /analyze the communication link degradation during his semester project.

The rotation rate of the satellite has been decreasing again, as shown on the time plot in the attached file. New simulations from Arthur, a student at TU Delft in the Netherlands doing his master thesis at ISIS, shows that the onboard controller could be turned on very soon. If the validity of his simulation is confirmed, commands will be sent to the satellite that will start the "b-dot" controller. That will slow down the satellite's rotation even faster.

Also, a new opportunity has arrived for increasing the operation's time thanks to the new sponsorship of EATOPS. EATOPS is creating the third official SwissCube ground station in the Netherlands, and will help operating the satellite. This comes as a great opportunity when manpower is brought down to its minimum on our side. We welcome EATOPS onboard the project although their collaboration is not totally new, since as they have worked in parallel with the project, producing a great visual and data software (RIVOPS) and also provided SwissCube with a state-of-the-art mission control set-up. We also welcome Yann on our side who will be helping with the mission operations and extending our uplink capability (and other technical improvements to the satellite). Yann will be working with us part time until he starts his master in Computer Science.

SwissCube survived also the close approach on January 5th and on February 5th with remnant debris of the collision between IRIDIUM and COSMOS. See a picture at the bottom of this post... It turns out also that the country of Equator was also concerned by atmospheric reentry and possible landing in their country and, thanks to them, we could follow live the close approach of January 5th. We hereby express our gratitude to Cmd. Ronnie Nader for setting up the link.

We have spend the last few weeks (or should I say months!) repairing our ground stations. At EPFL especially, we have seen the failure of the Elevation rotator and controller, and then of the Azimuth controller. This has significantly impaired our ability to communicate with the satellite. We also had to move the whole station to another floor of the building the ground station is in, and that created some perturbations and "re-alignments"...

In the upcoming month (of May), we will continue the repair of the ground station at EPFL, and a few minor things on the ground station at Fribourg, and then we will get ready for trying out the control strategy proposed by Arthur (TU Delft/ISIS). That will require the success of several commands and probably the contribution of RA outside Europe. But that should be fun to implement. More on that soon.

This latest news pushed the priority for writing this email to its highest! We received yesterday an email from the US Air Force stating:
"The United States Joint Space Operations Center (JSpOC) has identified a predicted close approach between SWISSCUBE (SCC# 35932) and SCC #34891. Please see the attached document for further conjunction specifics."
Following that email, Reto, one of the team members, put together a simulation of the possible collision between SwissCube and a debris coming from the IRIDIUM/COSMOS collision last year... The closest approach is supposed to be at around 500 m, but the errors on the knowledge of the position of both elements is greater than that. And the two objects are supposed to encounter tomorrow morning, Friday at 6h20 our time. This news really stresses the problem that the orbital debris are causing, and the dramatic increase in the density of the debris since the last 10 years or so does not help. Attached a small movie of tomorrow's close encounter, and a picture of the actual problem in a broader view (thanks Reto!). Although the probability of collision is still small, this news has come as a shock to us...

Otherwise, the satellite is still alive (beyond the 4 month of its operational lifetime), doing quite well and sending us data. A very good news is that its rotation has decreased to half of its initial value, we are now in the 180 deg/sec range. A few more weeks and we will be able to turn on the on-board detumbling algorithms... great news! The first picture should come soon after (a few weeks again), although it is hard to predict when exactly. I will keep you informed when we get closer to that day.

We will be impatiently waiting for a signal of SwissCube tomorrow, at the 11h48 pass over Switzerland...